React Performance Monitoring

See component render time and understand performance bottlenecks

Why is performance monitoring important for React?

Performance is one of the top cited reasons for why React has gained so much popularity. When it comes to options for building a web application React has many advantages in terms of performance. Some of React’s performance highlights include the ability to create single page apps, progressively load components, minimize costly DOM operations, the size of the library (just 43kb gzipped), using a virtual DOM, and minimizing the client’s resource load.

Even the most perfectly configured and performance-optimized React app should be monitored for performance. As an application becomes more complex, relies on more dependencies, or uses more third-party software, the likelihood of performance suffering grows. 

React performance monitoring in the backend

React is almost exclusively hosted on Node servers, therefore, performance monitoring for React on the backend is really just an exercise in Node logging. Some things to look out for include CPU usage, heap usage, memory leaks, long tasks, and garbage collection.  

While a slow node instance will undoubtedly slow down a React app, when we think of React performance monitoring, we are more focused on the front-end and React itself. But first, there are some general front-end performance monitoring methods that apply to all apps, not just React. 

Baseline React performance monitoring

There are some very basic key metrics that can give clues into the performance of a React app. Regularly testing, tracking, and monitoring aspects such as page load time, time to first byte, and slow network requests are the bare minimum when it comes to performance monitoring. Page load time is the most simple, but most important metric when it comes to performance. It has been proven that a long page load time leads to users exiting the application. There’s plenty of methods to capture these metrics, from using Chrome’s lighthouse, to open source monitoring tools, to paid solutions. 

React-specific Performance Monitoring: 

Due to the nature of how React works, performance issues typically are isolated to individual components and therefore are less likely to slow down an entire application. This also means that performance monitoring for React mostly revolves around components rather than the application itself. Some common issues with components that will affect performance include: 

  • component mounts
  • deep component trees
  • unnecessary render cycles

There are a number of performance-oriented tools that every React developer should be comfortable with. The two most important are the built-in perf functionality and the React Dev Tools Chrome extension

  • Perf is a profiling tool which is only available in development mode. It’s essentially a wrapper for specific components to log their performance such as mount time and render time. 
  • React Dev Tools is a handy tool for inspecting apps in development or production. The profiler tool provides a visual method to show how long a component and its children took to render. 

In addition to the built-in tools, a quick search for “React performance” on Github yields 852 repositories. Some of these add-ons extend React to offer performant functionality tailored to React, or make frequent operations like rendering large lists more performant. 

While these tools are all helpful for performance monitoring applications in development environments, monitoring performance in production is more difficult, and more important. Avoiding the “works on my machine” mentality is important when it comes to performance. Solutions like LogRocket enable you to monitor React performance for your real users, rather than just in development. You can track things like “show me all sessions where component X took longer than 2 seconds to render”. If you’re interested in leveling-up your React performance monitoring, get a free trial of LogRocket today.

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React Performance Monitoring